Session 5 Notes

Question 1

Define haemopoiesis?

Answer 1

The process by which blood cells are formed

Question 2

How many different lineage pathways arise from the haemopoeitic stem cells?

Answer 2

5

Question 3

What are the different lineage pathways that arise form the haemopoeitic stem cells?

Answer 3

Thrombopoiesis, granulopoiesis, monocytopoiesis, lymphopoiesis and erythropoiesis

Question 4

What does thrombopoiesis result in?

Answer 4

Formation of platelets

Question 5

What does the process of granulopoiesis result in?

Answer 5

Production of granulocytes

Question 6

What are granulocytes?

Answer 6

Basophils, neutrophils and eosinophils

Question 7

How are granulocytes produced?

Answer 7

Arise from myeloblast cells which in turn arise form common myeloid progenitor cells

Question 8

What has inappropriate activation of eosinophils been associated with?

Answer 8

Asthma and allergy

Question 9

What happens to monocytes after they are produced?

Answer 9

They circulate in the blood for 1-3 days before moving into tissues where they differentiate into macrophages or dendritic cells.

Question 10

What does the final maturation of B cells require?

Answer 10

Exposure to antigen in the lymph nodes

Question 11

Where do T cells mature?

Answer 11

Thymus gland

Question 12

What is erythropoiesis?

Answer 12

The process by which red blood cells are produced in the bone marrow

Question 13

What is the lifespan of an erythrocyte?

Answer 13

120 days

Question 14

What commits progenitor cells in the bone marrow to the erythroid lineage?

Answer 14

The expression of transcription factors GATA1, FOG1 and PU.1

Question 15

What happens once the progenitor cells are committed?

Answer 15

Further expansion of the erythroid precursors driven by the hormone erythropoietin

Question 16

Where is erythropoietin produced?

Answer 16

Kidney

Question 17

What increased erythropoietin production?

Answer 17

Decreased level of oxygen in the bloodstream

Question 18

What is the main function of erythropoietin?

Answer 18

Inhibit apoptosis of CFU - E progenitor cells

Question 19

What does CFU-E stand for?

Answer 19

Colony forming units of the erythroid cell line

Question 20

What does reticulocyte count from a blood sample show?

Answer 20

Provides a good diagnostic estimate of the amount of erythropoiesis occurring in a patient’s bone marrow

Question 21

How are reticulocytes formed?

Answer 21

Activation of CFU-E progenitor cells causes them to develop, proliferate and differentiate. During this process nucleated erythroblastosis extrude their nucleus and mots of their organelles hence forming reticulocytes.

Question 22

What is the role of the reticuloendothelial system?

Answer 22

Remove dead or damaged cells and to identify and destroy foreign antigens in blood and tissues

Question 23

What role does the spleen play in the RES?

Answer 23

It filters blood to remove deformed and old cells from the circulation

Question 24

When might a spleen be removed?

Answer 24

In response to trauma or to treat diseases such as hereditary spherocytosis

Question 25

What issues can people who don't have a spleen face?

Answer 25

Increased risk of sepsis

Question 26

Describe the red blood cell membrane

Answer 26

Lipid bilayer that contain proteins such as spectrum, ankyrin, band 3 and protein 4.2

Question 27

What do the proteins in the erythrocyte membrane do?

Answer 27

They facilitate vertical interactions its the cytoskeleton of the cell which are essential for maintaining the biconcave shape.

Question 28

What do gene mutations in the erythrocyte membrane proteins result in?

Answer 28

Diseases such as heriditary spherocytosis

Question 29

What deceases the affinity of haemoglobin for oxygen?

Answer 29

2,3 bisphosphoglycerate, fall in pH or increase in CO2.

Question 30

What happens to the oxygen dissociation curve if the affinity of haemoglobin for oxygen is decreased?

Answer 30

Rightward shift of the oxygen dissociation curve

Question 31

Why is free iron toxic to cells?

Answer 31

Because it acts as a catalyst in the formation of free radicals from reactive oxygen species

Question 32

Where does absorption of iron occur?

Answer 32

Duodenum and upper jejunum

Question 33

What facilitates the uptake of non-haem ferrous iron from the intestinal lumen?

Answer 33

Transporter protein divalent metal transporter 1 (DMT1)

Question 34

Where is DMT1 located?

Answer 34

On the apical surface of enterocytes

Question 35

What happens to ferric iron before uptake?

Answer 35

Reduced to ferrous iron

Question 36

What is responsible for reducing the ferric iron to ferrous iron?

Answer 36

Duodenal cytochrome B reductive (DcytB)

Question 37

What is the absorption of iron regulated by?

Answer 37

Small peptide called hepcidin

Question 38

What are the two forms in which iron can be stored?

Answer 38

Ferritin and its insoluble derivative haemosiderin

Question 39

What is ferritin?

Answer 39

It is a protein-rich complex which can be incorporated by phagolysosomes to form haemosiderin granules.